Field of the Invention
The present invention relates to a linear actuator.
The Prior Art
A common type of actuator is, e.g., known from EP 531 247 A1 Linak A/S. The forces occurring on the spindle are here absorbed by a compressive/tensile bearing embedded in a plastic housing, The forces occurring between the bearing and the rear mounting are transferred through the plastic housing, which should thus be dimensioned and designed accordingly. Such a plastic housing thus constitutes a major share of the price of the actuator.
EP 1 922 797 A1 Linak A/S likewise discloses a common type of linear actuator comprising a two-part housing containing all the components of the actuator, i.e., the electric motor, the transmission, the spindle, the spindle nut, the outer tube and the rear mounting. The forces from the spindle are transferred to the housing through a compressive/tensile bearing located between the spindle and the transmission. Due to the relatively large proportions of the housing and the fact that this should be able to absorb the forces transmitted from the spindle, the housing must constitute a particularly sturdy structure. Consequently, this two-part component constitutes a large share of the total costs of the actuator.
A more recent and special type of linear actuator is disclosed in EP 1 322 876 A1 Linak A/S. This type is cheaper to manufacture, but has a corresponding output and quality. Here the linear actuator is designed such that a console on the motor housing is equipped with a fixing for the outer tube, the spindle bearing and the rear mounting, which is designed for absorbing the forces occurring thereon. The console is solely designed for transferring the forces between the bearing and the rear mounting and should otherwise be as compact as possible. The motor housing and the console thus constitute the main portion of the actuator, or in other words, the chassis, Unlike the linear actuator in EP 1 922 797 A1 Linak A/S, the housing of the linear actuator disclosed in EP 1 322 876 A1 Linak A S is not exposed to the same forces, for which reason there are no particular strength requirements for the housing. Thus, the manufacturing and design thereof becomes more uninhibited. The material thickness of the housing may thus be thin, and stiffening ribs may in all essentials be left out, resulting in a simpler mould tool and an easier and thus cheaper manufacturing, Further, less strong types of plastic may be chosen, which per se are cheaper but also advantageous in terms of production. Though the linear actuator disclosed in EP 1 322 876 A1 Linak A/S reduces the costs of the housing and simplifies the assembly process as a result of the console, these improvements only contribute to a marginal reduction of the total cost of the product.
The present invention relates to the problem of providing a linear actuator which on the one hand is more cost efficient and on the other hand is more production-friendly.